1. Technical Field
The present invention relates to an electro-optical device that is suited to display images with high definition and to an electronic apparatus.
2. Related Art
In general, electro-optical devices, for example, liquid crystal devices for displaying images, which use liquid crystal as an electro-optical material, include a pair of substrates and liquid crystal interposed between the pair of substrates. Of these devices, an electro-optical device such as an active-matrix-type liquid crystal device which is driven by thin film transistors (TFTs), thin film diodes (TFDs) or the like includes a plurality of scanning lines and data lines which are arranged in vertical and horizontal directions, a plurality of pixel electrodes disposed at intersections of the plurality of scanning lines and the plurality of data lines, and the like. All of them are arranged on a TFT array substrate.
The scanning lines are sequentially supplied with scanning signals from a scanning line driving circuit. On the other hand, the data lines are supplied with image signals from a sampling circuit which is driven by a data line driving circuit. That is, the data line driving circuit supplies a sampling circuit driving signal to the sampling circuit which samples the image signals on image signal lines for each data line, simultaneously with the sequential supply operation of the scanning signals.
In general, the data line driving circuit includes a plurality of latch circuits (shift register circuits) that sequentially shift transmission signals, which are supplied at the beginning of a horizontal scanning period, according to a clock signal and that output the shifted signals as the sampling signals. Likewise, the scanning line driving circuit includes a plurality of latch circuits that sequentially shift transmission signals, which are supplied at the beginning of a vertical scanning period, according to the clock signal and that output the shifted signals as the scanning signals. In addition, the sampling circuit includes sampling switches which are provided for the respective data lines so as to sample the image signals, which are supplied from the outside, according to the sampling signals output from the data line driving circuit.
In the meantime, recently, in compliance with the general demand for quality improvement of display images, the pixel pitch has been reduced more and more, which causes the driving frequency to increase.
However, when the driving frequency is increased in such a simple method where the transmission signals sequentially output from the shifter circuit are used as the sampling signals, a sampling time assigned for the sampling circuit becomes short. This may result in deterioration of the sampling capability in the sampling circuit. In this regard, in order to enhance transistor characteristics of the TFTs constituting the sampling circuit or wiring line characteristics of various wiring lines, such as resistance, time constant, and the like, the production cost may be increased or the yield reduced.
Recently, as a countermeasure against a high-frequency dot clock, a group of image signals is subjected to serial-parallel conversion to form a plurality of m groups. More specifically, a technique in which the simultaneous sampling operation of the m groups of image signals is performed according to the sampling signals, together with ‘phase expansion’, and the sampled image signals are supplied to m data lines has been developed. That is, a technique in which driving control based on ‘phase expansion’ is performed using image signals divided into m (where m is a natural number of 2 or more) parallel data sequences for the phase expansion has been developed. The number of data sequences into which the image signals are divided by the phase expansion is, for example, 6, 12, 24, or the like. In addition, in the case of color image signals, if the image signals of the m data sequences subjected to the phase expansion have n colors (where n is a natural number of m or less, for example, 3 in the case of three RGB colors), respectively, each of the image signals becomes n parallel color signals. In this case, the image signals of one data sequence mean a set of n (for example, 3) image signals.
In general, for example, when one pixel has three RGB subpixels for a color image display, the conversion operation of a color image signal into three RGB parallel image signals is sometimes called ‘phase expansion’ or ‘serial-parallel conversion’ in a broad sense. In this case, the three RGB image signals as image signals of subpixels belonging to the same pixel are defined as image signals of ‘different data sequences’, and one image signal is constantly converted into three image signals through the phase expansion or the serial-parallel conversion.
However, in this specification, in the case of the color image signals, the three RGB image signals serving as image signals of subpixels belonging to the same pixel are defined as image signals of the ‘same data sequence’. More broadly, in this specification, parallel image signals belonging to the same pixel or the same group of pixels are defined as image signals of the ‘same data sequence’ or ‘one data sequence’. That is, in this specification, ‘phase expansion’ or ‘serial-parallel conversion’ means the conversion operation of an image signal into parallel image signals belonging to different pixels. For example, in the case of the color image signals, the image signals of one data sequence after the phase expansion have a set of three RGB color image signals as image signals of subpixels belonging to the same pixel.
Moreover, the above-described phase expansion is disclosed in Japanese Unexamined Patent Application Publication No. 2004-46201 and other publications.
However, recently, with an increasing need for images with high definition and reduction of the pixel pitch, it is required to arrange a plurality of scanning lines and data lines at narrow pitches on a display panel and to drive these lines at a high frequency.
In addition, it is required to increase the number of image signal lines on the display panel by the number of phase expansions. In particular, in order to display color images in which one pixel has, for example, three RGB subpixels, three image signal lines per one pixel are required. Accordingly, it is required to form image signal lines whose number is given by the number of phase expansions×3.
In such a manner, the number of image signal lines for the phase expansion formed on a substrate increases. In particular, in the case of a plurality of image signals for the same pixel, such as image signals of subpixels, the number of image signal lines for the phase expansion formed on a substrate increases more and more. In addition, wiring lines of sampling circuit driving signal lines or the like which need to cross above or below the image signal lines become complex.
Therefore, there is a problem in that noise due to the effect of adjacent signal lines is not negligible.